Patent Literature (PTL) 1 (Japanese Patent No. 4732815) discloses a technique for providing information appropriate for the user by learning the user's preference from the user's information viewing history (viewing history of broadcast program, for example).
Furthermore, PTL 2 (Japanese Unexamined Patent Application Publication No. 2001-298677) discloses a technique for proposing not only a recommended program based on the history information but also a recommended program obtained by grouping people who have slimier preference and determining a program viewed by the greatest number of people out of the programs viewed by the people in the same group.